Indonesia is dealing with three natural disasters after an earthquake, a tsunami and a volcanic eruption in the space of 24 hours.

Rescuers battled rough seas yesterday to reach remote islands hit by a 10ft tsunami that swept away homes, killing at least 113 people. Scores more were missing and casualties are expected to rise as information trickles in from the sparsely populated surfing destination.

The fault that ruptured on Monday off Sumatra island's coast also caused the 2004 earthquake and Indian Ocean tsunami, which killed 230,000 people in a dozen countries.

Monday's 7.5 magnitude earthquake hit 48 miles west of South Pagai, in the Mentawai islands, and destroyed most of the buildings in the coastal village of Betu Monga, a Department of Fisheries official said.

Many panicked residents fled to high ground and were too afraid to return home. Hendri Dori, a local parliamentarian, said panic could account in part for the more than 500 people still missing. "We're trying to stay hopeful," he said.

Mujiharto, the head of the health ministry's crisis centre, said 113 bodies had been recovered so far. The number of missing was between 150 and 500. "We have 200 body bags on the way, just in case," he said.

A tourist boat carrying between eight and 10 Australians has been out of radio contact since the quake occurred, Australia's department of foreign affairs and trade said.

Hundreds of wooden and bamboo homes were washed away on the island of Pagai, with water flooding crops and roads up to 600 metres inland. In Muntei Baru, on Silabu island, 80% of the houses were badly damaged.

On the island of Java 800 miles away, Indonesia's most volatile volcano spewed out clouds of hot ash yesterday morning, killed at least 18 people, according to local reports.

Mount Merapi has been erupting since September, and scientists said the latest activity was almost certainly not triggered by the earthquake. Brian Baptie, a seismologist from the British Geological Survey, said: "Indonesia is one of the most seismically active places on Earth, so there's always going to be a chance of a volcano erupting around the same time as an earthquake."

Authorities had been trying since Monday to evacuate more than 11,000 villagers living on the volcano's slopes, after the alert status was raised to the highest level, but some people were unable to flee in time.

Scientists warned that pressure building beneath its dome could trigger the most powerful eruption in years. Surono, a government volcanologist, said: "The energy is building up … We hope it will release slowly. Otherwise, we're looking at a potentially huge eruption, bigger than anything we've seen in years."

Indonesia is prone to earthquakes and volcanic activity due to its location on the so-called Pacific Ring of Fire, a series of fault lines stretching from the western hemisphere through Japan and south-east Asia. There are more than 129 active volcanoes in Indonesia, which is spread across 17,500 islands.